1. Technical Field
The present invention relates generally to a pulse radar apparatus and, more particularly, to a pulse radar apparatus that is capable of receiving an echo signal returned from a target.
2. Description of the Related Art
A pulse radar sends transmission pulses at a pulse repetition frequency (PRF), and obtains information about a target by receiving an echo signal returned from the target and by analyzing the echo signal.
A conventional pulse radar receiver has a limitation to acquire high resolution because whether or not a pulse is present is determined based on a single transmission pulse and thus distance resolution is determined by pulse width. Although, among conventional pulse radar reception schemes, there is a scheme for increasing the Signal to Noise Ratio (SNR) of a received pulse by receiving a plurality of transmission pulses, this scheme also has a limitation to obtain high resolution.
In a conventional range gating method, delay is varied by disposing a delay element in the receiver of a radar, so that whether or not a target is present within a specific range is determined and then a range can be swept. However, this conventional range gating method has a limitation in the improvement of the resolution of a range that is determined by a pulse width.
As a related technology, U.S. Pat. No. 5,805,110 entitled “Impulse Radar with Swept Range Gate” discloses a structure in which a specific range can be variably determined.
In the technology disclosed in U.S. Pat. No. 5,805,110, a receiver is operated by delaying the signal of a pulse generator and inputting the delayed signal to a range gate, and thus the receiver is operated as a variable range receiver.
As another related technology, U.S. Pat. No. 7,675,459 entitled “Equivalent Time Sampling Radar” discloses a technology in which a reference signal is dithered using a noise signal and input pulses are sampled using the dithered signal, together with a sweep signal generator.
In the technology disclosed in U.S. Pat. No. 7,675,459, transmission pulses are generated using a signal obtained by dithering a reference clock, sampling pulses are generated using a sweep signal generator and a transmission dithering signal, and a signal received from a target is received by a sampling and hold circuit.